Gas range burner assembly

ABSTRACT

The gaseous fuel as it is delivered to the burner is heated to expand the same and compensate for expansion of the combustion air which occurs and alter the gas-air ratio. In an oven with a heat exchanger, in which air supplied to the oven burner and the oven exhaust are brought into heat transfer relation, the exhaust is directed over a heat section in the fuel line to the burner to effect the desired fuel temperature rise.

United States Patent Inventor Richard L. Perl Mansfield. Ohio App1.No.815,924

Filed Apr. 14, 1969 Patented July 6, 1971 Assignee The 'lappln CompanyMansfield, Ohio GAS RANGE BURNER ASSEMBLY [56] References Cited UNlTEDSTATES PATENTS 3,199,568 8/1965 Baumanns et a1 431/215 3,416,509 12/1968Huebler et al. 126/21 A Primary ExaminerCharles J. MyhreAttorney-Oberlin, Maky,Donne1ly and Renner ABSTRACT: The gaseous fuel asit is delivered to the burner is heated to expand the same andcompensate for expansion of the combustion air which occurs and alterthe gas-air ratio. In an oven with a heat exchanger, in which airsupplied to the oven burner and the oven exhaust are brought into heattransfer relation, the exhaust is directed over a heat section in thefuel line to the burner to effect the desired fuel temperature rise.

PATENTED JUL 6 I971 SHEET 1 BF 2 INVENTOR RICHARD L. PERL JQTTORNEYSPATENTEDJUL 6l97i 3.590.805

sum 2 or 2 INVENTOR 5.257. E R/CH/JRD L. PERL ATTORNI'IYS GAS RANGEBURNER ASSEMBLY This invention concerns gas range burners, particularlyof the type powered by supply of the combustion air under pressure aswell as the gaseous fuel, and the firing of such burners.

There are range applications for such burners in which the supply airbecomes significantly heated as a result of operation of the burner,either by design or unavoidably, and the resulting expansion-reductionin the weight of the air mixed with the fuel causes the mixture tobecome relatively rich. Since this condition could be hazardous, somecompensation should be provided, and the obvious answer would be toadjust the starting ratio, that is, upon ignition at room temperature,for supply of excess air in an amount that will be more than enough tooffset the loss through heating. The mixture in this case must ignitehard" or while quite lean, and the excess of cold (room temperature) airextends the heating-up period.

The present invention provides another and much more advantageoussolution by regulating the firing of the burner so that the mixture isinitially rich and the weight of the fuel is restricted in the operationof the burner. in a reversal of the above-described approach, themixture ignites "soft" and the initial heat rate is higher than normalfor rapid heating to operating temperature. The efficiency of suchoperations as broiling and radiant heating more generally can bebenefited materially in this respect.

It is also a principal object to provide such a burner assembly which isregulated in an extremely simple and economical manner. The economy ofuse of the invention is obviously of substantial practical importance,while the simplicity of design is a factor also in the reliability ofthe control which is exercised.

An additional object of the invention is to provide such a burnerassembly in which the regulation is responsive to the heat output of theburner and the operation is self-limiting. The reduction of the rate ofheating in response to the operation of the burner, and specifically theenvironmental heating produced by the same, introduces an inherentsafety in the assembly which can, for example, in an oven protect theenamel coating the interior surfaces of the oven liner from overheating.In a range top in which there is a glass support above a radiant heater,as another example, the limiting feature can be utilized to make surethat the temperature of the glass does not exceed the maximum designvalue.

It is a further object to utilize such a regulated burner in conjunctionwith a heat exchanger in which the supply air to the burner and theheated products from the same are brought into heat transfer relationfor preheating of the former and cooling of the latter. Such a burnerand exchanger combination has been applied to self-cleaning ovenconstruction for heating the cavity to a temperature of about 950 F. toeliminate food soil therein while limiting the exhaust to about 250 F.,and the burner is regulated to establish and maintain nearstoichiometric mixing of the air and fuel. This ratio is initially setby adjustment of the start mixture at room temperature and is maintainedby proportionately reducing the fuel supply as the air temperature risesand its weight decreases. Excess air can thus be held to a practicalminimum, and this is a very significant factor in holding the exhaust tothe indicated low temperature for relatively cool kitchen operationnotwithstanding the extremely high cleaning temperature within the oven.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawing setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principle ofthe invention may beemployed.

In said annexed drawing:

FIG. 1 shows in a simplified and partially fragmented perspective theburner system of a domestic gas oven in which the upper or broil burnerassembly is in accordance with the present invention; and

FIG. 2 is a fragmented elevation of such oven system at the rear of theburners on an enlarged scale.

Referring now to the drawings in detail, the dashed outline provides aphantom range environment for the oven system fully shown as comprisinga top broil burner 11 and a bottom bake burner 12. The broil burner,preferably of forced air radiant ceramic type or the equivalent, will ofcourse be arranged to provide radiant energy at the top of the cookingcavity formed by the linear means, not shown, while the bottom burnerwill be covered by the usual removable oven bottom having slots or otherperforations for flow upwardly of the heated products from the burnerthrough the cavity. The burners are shown as equipped for spark ignitionrespectively by ignitors l3 and 14.

An oven vent 15 is provided at a rear upper location relative to thecavity and leads to an exhaust duct 16 enclosed within and isolated froma vertically oriented air supply duct 17. The latter is in communicationwith both air inlets 18 and 19 for the top and bottom burners, the bakeburner as well being designed to operate with the pressurized airsupply.

At the rear of the oven wall 20, there is a stationary heat exchanger 21of general scroll form and having spiral alternating fresh air andexhaust passages. The inner central end of the exhaust passage 22communicates with an opening 23 in the exhaust duct 16 which is withinthe air supply duct 17, while the also inner central end of the freshair passage 22' communicates with a separate discharge opening 24through the air supply duct 17. From this center discharge, the airpassage 22' winds spirally outwardly to an air blower 25, and theexhaust passage 22 extends similarly in alternating turns to an exhaustblower 26.

The two blowers, which can be driven from a single motor, producecounterflows of the air and exhaust to the burners and from the cavity,respectively, and there is a continuation exhaust duct 27 which carriesthe heated products to a convenient room outlet 28 located in thebacksplasher of the range. The oven controls will be such that bothblowers are operative whenever either burner is turned on and, in aworking embodiment of thissystem, the bake burner alone is of courseused for baking and roasting operations and the broil burner is used notonly for broiling but also for self-cleaning, the latter operationinvolving heating the oven to a temperature on the order of 950 F. as iswell known.

The control of the range is exercised in part through a solenoidoperated gas valve 29 to which the gaseous fuel, usually natural gas, isdelivered under ordinary pressure through the line 30 and from which thefuel is selectively delivered at the same pressure either to the bakeburner through the line 31 or the broil burner through the further line32.

The supply line 31 to the top or broil burner 11 includes, however, aspecial heat section 32' shown as comprising two loops of the line ortubing and a mounting plate 33. This section is applied to theregenerator or exchanger 20 so that it is disposed in the passageleadingfrom the oven exhaust ducting 16 to the exchanger and hence isexposed to the exhaust or outflow of the heated products from the ovencavity.

The purpose of this section 32', which serves as a regulating device, isto effect a predetermined expansion of the gaseous fuel delivered to thetop burner proportional to the temperature in the oven cavity and henceits exhaust. As noted earlier, the air supply to the top burner duringbroiling or self-cleaning becomes heated by design as a result of thetransfer of heat energy between the same and the exhaust within theexchanger, especially during cleaning, to maintain the dischargetemperature at a level which can be very readily tolerated within a homekitchen, with the result that the weight of the air delivered forcombustion with the fuel decreases and themixture tends to becomerelatively rich or soft. This weight loss of air has been fullycompensated by the heating of the gaseous fuel which inheres in thearrangement shown with temperature rise in the oven, and it has beenpossibleto maintain nearly stoichiometric values throughout even thefairly lengthy and high temperature cleaning operation.

More particularly, in a typical clean cycle in an oven operated withnatural gas at normal pressure, the broil burner has been operated at aninitial rate of 23,200 B.t.u./hour with the oven at a temperature of 120F. and the temperature of the tube heater section at 1 F. The finalburner rate, at the maximum design temperature of 920 F., was 17,250B.t.u./hour realized with a tube heater section temperature of 550 F.Accordingly, it is not necessary in this system that the powered radiantburner be ignited hard or with excessive air when cold in order toprotect against the mixture becoming dangerously rich at the maximumtemperature of the oven, and the self-regulating feature is realizedobviously without complication or significant added expense. Thetemperature rise of the fuel is of course matched in this control to thetemperature increase of the air to maintain the .proper gas-air ratio,but the manner in which the fuel is heated might vary considerably bothwhere the heated products of the burner are used for the purpose andalso with different heat sources employed, for example, auxiliary heatinputs. Cost is a factor in this last respect, with the particularconfiguration or assembly used, however, ensuring that the fueltemperature will experience quickly the desired temperature rise.

Having determined that the reduction in fuel weight would be highlydesirable for the noted reasons, the simplicity of the disclosedembodiment will be further appreciated by considering some possiblefunctional alternatives. For example, the air fan capacity could be madeto increase as the oven temperature rises, but this would require anautomatic motor control. A damper might also be used for increasing theair supply with temperature rise, but this expedient again requires theaddition of a temperature sensitive device and mechanical actuation. Thedisclosed solution, on the other hand, only requires the appropriatematching of the fuel temperature rise relative to the decreasing airsupply with constant fan speed and the same fixed orifice.

I, therefore, particularly point out and distinctly claim as myinvention:

1. In a gas burner system in which a combustible mixture of a gaseousfuel and air is burned for heating purposes, with the mixture relativelyrich at ignition and the combustion air experiencing an appreciabletemperature rise following ignition and heating of the burner tooperating condition, such that the mixture tends to become increasinglyrich, means for compensating for the weight loss of the combustion airresulting from such temperature rise of the same to prevent suchincrease in the richness of the mixture, said means comprising a sourceof the gaseous fuel under pressure, fuel supply means extending fromsaid source to the burner to convey the fuel to the latter forcombustion, and means for heating the fuel to raise its temperature asit is conveyed by the fuel supply means to reduce the fuel weightproportional to said weight loss in the combustion air supplied to theburner.

2. A gas burner system as set forth in claim 1, wherein said heatingmeans is powered by a portion of the heat produced by the burner.

3. In combination with a gas burner in which a combustible mixture of agaseous fuel and air is combusted for heating purposes, with the mixturerelatively rich at ignition, enclosure means for the burner whichbecomes heated thereby, a source of the gaseous fuel under pressure,fuel supply means including a delivery line for conveying the fuel fromthe source to the burner, means for supplying combustion air to theburner with the air experiencing an appreciable rise in temperature insuch supply as a result of operation of the burner and the fuelair ratioas a result tends to become increasingly rich, and means for applyingheat to a portion of said delivery line to effeet a compensating rise inthe temperature of the fuel therein and prevent such relative increasein the richness of the mixture.

4. The combination set forth in claim 3, wherein heat energy within saidenclosure means is applied to the heating ofsaid delivery line.

5. The combination set forth in claim 4, wherein said portion of thefuel delivery line is exposed within the enclosure means for the heatingof the former.

6. The combination set forth in claim 3, wherein the means for supplyingcombustion air to the burner includes a blower for delivering the airthereto under pressure.

7. The combination set forth in claim 6, wherein the combustion air inthe supply thereof to the burner is brought into heat exchange relationto heated products exhausted from the burner for cooling of suchproducts and preheating of the air.

8. The combination set forth in claim 7, wherein the enclosure means forthe burner forms an oven cooking cavity.

9. The combination set forth in claim 8, wherein said portion of thedelivery line for the fuel is exposed to exhaust of the heated productsfrom the oven cavity for the heating of the fuel in the supply thereofto the burner.

10. The combination set forth in claim 7, wherein said portion of thefuel delivery line is exposed to the heated products exhausted from theburner prior to the bringing the latter into the heat exchange relationto the combustion air.

11. The method of regulating operation of a burner in which a mixture ofa gaseous fuel and air is combusted for heating purposes, with themixture relatively rich at ignition, and the combustion air in thesupply of the same to the burner experiencing an appreciable temperaturerise following ignition of the burner and heating of the same tooperating condition, whereby the mixture tends to become increasinglyrich, which comprises the steps of establishing a source of the gaseousfuel under pressure remote from the burner, heating the fuel in deliveryof the same to the burner from said source to reduce the weight thereofin the combustible mixture, and relating such heating of the fuel to theaforesaid heating of the combustion air to compensate for the weightloss of the latter and prevent the noted increase in the richness of themixture that would otherwise occur.

12. The method set forth in claim 11, wherein a portion of the heatgenerated by the burner is applied to the heating of the fuel in thedelivery of the same to the burner.

1. In a gas burner system in which a combustible mixture of a gaseousfuel and air is burned for heating purposes, with the mixture relativelyrich at ignition and the combustion air experiencing an apprEciabletemperature rise following ignition and heating of the burner tooperating condition, such that the mixture tends to become increasinglyrich, means for compensating for the weight loss of the combustion airresulting from such temperature rise of the same to prevent suchincrease in the richness of the mixture, said means comprising a sourceof the gaseous fuel under pressure, fuel supply means extending fromsaid source to the burner to convey the fuel to the latter forcombustion, and means for heating the fuel to raise its temperature asit is conveyed by the fuel supply means to reduce the fuel weightproportional to said weight loss in the combustion air supplied to theburner.
 2. A gas burner system as set forth in claim 1, wherein saidheating means is powered by a portion of the heat produced by theburner.
 3. In combination with a gas burner in which a combustiblemixture of a gaseous fuel and air is combusted for heating purposes,with the mixture relatively rich at ignition, enclosure means for theburner which becomes heated thereby, a source of the gaseous fuel underpressure, fuel supply means including a delivery line for conveying thefuel from the source to the burner, means for supplying combustion airto the burner with the air experiencing an appreciable rise intemperature in such supply as a result of operation of the burner andthe fuel-air ratio as a result tends to become increasingly rich, andmeans for applying heat to a portion of said delivery line to effect acompensating rise in the temperature of the fuel therein and preventsuch relative increase in the richness of the mixture.
 4. Thecombination set forth in claim 3, wherein heat energy within saidenclosure means is applied to the heating of said delivery line.
 5. Thecombination set forth in claim 4, wherein said portion of the fueldelivery line is exposed within the enclosure means for the heating ofthe former.
 6. The combination set forth in claim 3, wherein the meansfor supplying combustion air to the burner includes a blower fordelivering the air thereto under pressure.
 7. The combination set forthin claim 6, wherein the combustion air in the supply thereof to theburner is brought into heat exchange relation to heated productsexhausted from the burner for cooling of such products and preheating ofthe air.
 8. The combination set forth in claim 7, wherein the enclosuremeans for the burner forms an oven cooking cavity.
 9. The combinationset forth in claim 8, wherein said portion of the delivery line for thefuel is exposed to exhaust of the heated products from the oven cavityfor the heating of the fuel in the supply thereof to the burner.
 10. Thecombination set forth in claim 7, wherein said portion of the fueldelivery line is exposed to the heated products exhausted from theburner prior to the bringing the latter into the heat exchange relationto the combustion air.
 11. The method of regulating operation of aburner in which a mixture of a gaseous fuel and air is combusted forheating purposes, with the mixture relatively rich at ignition, and thecombustion air in the supply of the same to the burner experiencing anappreciable temperature rise following ignition of the burner andheating of the same to operating condition, whereby the mixture tends tobecome increasingly rich, which comprises the steps of establishing asource of the gaseous fuel under pressure remote from the burner,heating the fuel in delivery of the same to the burner from said sourceto reduce the weight thereof in the combustible mixture, and relatingsuch heating of the fuel to the aforesaid heating of the combustion airto compensate for the weight loss of the latter and prevent the notedincrease in the richness of the mixture that would otherwise occur. 12.The method set forth in claim 11, wherein a portion of the heatgenerated by the burner is applied to the heating of the fuel in thedelivery of the same to the burner.